There are objects in the database, which can provide drinking water. To indicate this feature you can use this tag. For example a public toilet may provide drinking water. The same applies to wells or mountain huts. As such this is one of the few OSM tags that can indicate the _lack_ of a feature you might otherwise expect (for example the rare highway rest area that does not supply drinking water, or the rare mountain hut where you must carry water to).

In other cases you can subtag an existing object (like a fountain) with the info that the water is drinkable.

How to map

The water is drinkable for humans and animals. There must be objective reasons that allow you to conclude that the water is pure. E.g. in alpine territory the source can be above any civilization. One can assume that the water is pure when many people drink it every day.

There is no warranty for this tag. The circumstances can change every day. Everyone should use his common sense before drinking water from unknown sources.

If there is a label "No drinking water" because there is no official control, you can tag additional drinking_water:legal=no.

no

There exists no drinking water.

The water is not drinkable. It is obvious that the water is soiled or contaminated or flows through a circulating pump.

In some countries a label "No drinking water" is not sufficient to tag no. It is possible that every source without official control gets this label, although the water is drinkable. You can tag additional drinking_water:legal=no.

conditional

The water seems drinkable. You can drink it at your own risk.

If there is a label "No drinking water" because there is no official control, you can tag additional drinking_water:legal=no.

treated

It's about water that has been disinfected, for example, with a bit of chlorine, ozone ... to kill potential pathogens germs, especially in summer and climate with high temperatures. It is a cheap, very efficient and common way of treating water. See Water treatment and Water purification.

untreated

Water quality is unknown. Because you do not know too much about where water was obtained rather not from the water supply network. Maybe from the well in the village.